The present invention relates to sprinkler units, and pertains particularly to an improved containment ring for pop-up sprinkler units.
Pop-up sprinkler units are widely used in both residential and commercial applications to irrigate lawns and shrubs. They typically include a riser that is axially retracted into a fixed outer cylindrical housing buried in the ground when not in use, and which extends from the outer housing to a position above the surface of the ground when water pressure is applied. The top of the riser is level with the ground when retracted. Seals inside the housing wipe the surface of the riser as it extends from, and retracts into, the housing.
In many applications of retractable sprinkler units, such as playing fields, golf courses and the like, it is important that the tops of the risers of the sprinkler units reliably retract to a position level with the surface of the playing field, so that they not become obstacles. However, the typical riser of a conventional retractable sprinkler unit frequently jams or sticks in a partially retracted position. This usually occurs when dirt and debris get between the seals and the surface of the retractable riser. This often results in the riser being stuck, i.e. it will not retract.
In a conventional pop-up sprinkler unit the riser and its retraction spring and seals are assembled into the fixed outer housing from the top. These components are typically retained in place by a plastic containment spring which snaps into an annular groove at the top of the fixed outer housing. The containment ring is split so that it can be compressed inward in diameter and inserted into the upper end of the bore of the fixed outer housing. The resilient ring is then allowed to expand to engage in the annular groove in the housing bore to retain the riser in the housing. The containment ring has a sufficient gap at its split to enable the ring to be compressed in diameter sufficiently to be inserted in the bore of the outer housing. When the containment ring expands into the annular groove, the vertical opposing faces or ends of the ring spread apart, leaving a gap which allows dirt and debris to enter the outer housing. The dirt and debris can work its way between the seals and riser. This can damage the seals and/or cause the riser to jam.
It is, therefore, desirable that an improved simple and effective containment ring be available to hold a riser inside the fixed outer housing of a pop-up sprinkler unit.